JP2018034077A - Method for operating membrane separation device and membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating a membrane separation device capable of dealing with an unexpected rapid differential pressure rise while attaining the reduction of operation cost by increasing engineering flux.SOLUTION: Provided is a method for operating a membrane separation device where the water to be treated is subjected to solid-liquid separation via a separation membrane, comprising: a membrane filtration step where, a permeable water amount M (t) from the membrane separation device is set to satisfy the relation represented by the numerical formula M(t)=KQ(t-1); where M(t) denotes the permeable water amount in a time t with a prescribed length; K denotes a gain (>1); and Q(t-1) denotes the inflow amount of the water to be treated in a time t-1 immediately before the time t, and permeable water is pulled out from the membrane separation device at the set permeable water amount; and a stop step where, when the water level of a water tank immersed and arranged with the membrane separation device is reduced to a pre-set stop water level, the pulling out of the permeable water from the membrane separation device is temporarily stopped.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for operating a membrane separator and a membrane separator.

  Patent Document 1 discloses sewage that employs a membrane separation activated sludge method in which a membrane separation device for solid-liquid separation of an activated sludge mixed liquid in a tank is immersed in an aeration tank that biologically treats organic sludge with activated sludge. A processing unit is shown.

  The sewage treatment apparatus includes sewage transfer means for transferring organic sewage to the aeration tank at a flow rate that satisfies the daily average sewage amount so that gravity filtration can be efficiently performed while maintaining the water level in the tank within a substantially constant range. In addition, a constant flow discharge means for discharging a membrane permeate equivalent to the daily average amount of sewage is provided, and the sewage transfer means and the constant flow discharge means are configured to work together.

  In other words, in either gravity filtration or suction filtration, the difference between the amount of sewage flowing into the aeration tank and the amount of permeable membrane permeate so that the water level of the aeration tank in which the membrane separation device is immersed is maintained constant. Was adjusted so that the amount of inflow sewage and the amount of outflow membrane permeate were equal.

Japanese Patent Laid-Open No. 10-15573

  In such a membrane separation apparatus, when the membrane surface is contaminated with filtration and the differential pressure on the membrane surface, that is, the permeation resistance value (hereinafter also referred to as “transmembrane differential pressure”) increases, In such a case, the filtration operation is stopped and the membrane surface is washed by the upward flow of the water to be treated by aeration, since the permeated water amount, that is, the permeation flux (hereinafter also referred to as “flux”) decreases. In addition, it was necessary to remove dirt from the film surface by washing with a chemical solution such as sodium hypochlorite.

  When relaxation or chemical cleaning is performed, filtration is delayed during this period.Conventionally, the design flux has a considerable margin to suppress the sudden increase in differential pressure, and at the time and time when the inflow of sewage is reduced. The administrator manually cleans the filter membrane by manually operating pumps and valves.

  In order to secure a predetermined amount of permeated water with such a design flux, it is necessary to increase the membrane area, that is, to increase the number of installed membrane separation devices, resulting in increased operating costs such as power costs required for aeration and the like. It was.

  In order to reduce the operating cost of wastewater treatment facilities using such a membrane separation activated sludge method, it is necessary to reduce the membrane area of the installed membrane separation apparatus and increase the design flux.

  However, if the membrane area is reduced and the design flux is increased, the permeation resistance value may increase unexpectedly. In such a case, the membrane surface should be cleaned immediately while securing a predetermined amount of permeated water. You need to be able to do it. That is, it is necessary to forcibly create time for removing the film surface resistance during normal operation.

  In view of the above-described problems, an object of the present invention is to provide an operation method of a membrane separation apparatus and a membrane separation apparatus that can cope with an unexpected and sudden increase in differential pressure while increasing the design flux and reducing the operation cost. The point is to provide.

In order to achieve the above-mentioned object, the first characteristic configuration of the operation method of the membrane separation apparatus according to the present invention is that the treated water is passed through the separation membrane as described in claim 1 of the claims. A method for operating a membrane separation device for solid-liquid separation, wherein the permeated water amount M (t) from the membrane separation device is expressed by the following equation M (t) = KQ (t−1)
M (t): Permeated water amount in period t having a predetermined length K: Gain (> 1)
Q (t−1): set to have a relationship represented by the inflow amount of the water to be treated in the period t−1 immediately before the period t, and the permeated water is drawn out from the membrane separation device with the set permeate amount. Membrane filtration step, water tank in which the membrane separation tank device is immersed, water tank in communication with the water tank and having the same water level as the water tank, or overflow water from the water tank in which the membrane separation device is immersed And a stop step for temporarily stopping the extraction of the permeate from the membrane separation device when the water level of the water tank into which the water flows is lowered to a preset stop water level.

  The gain K is set to be larger than 1, and the permeated water amount M (t) in the period t with respect to the inflow amount Q (t−1) of the water to be treated in the period t−1 immediately before the period t is expressed by the above equation. By setting so as to be, a water tank in which the membrane separation tank device is immersed and placed over time during the execution of the membrane filtration step, or a water tank communicating with the water tank and having the same water level as the water tank, or A steady situation appears in which the water level of the water tank into which the overflow water from the water tank in which the membrane separation device is immersed is gradually lowered. In such a situation, when the stop step for temporarily stopping the extraction of the permeated water from the membrane separation apparatus is executed, the water level in the membrane separation tank gradually recovers, and in the meantime, it is possible to secure time for cleaning the separation membrane. Thus, it is possible to cope with an unexpected sudden increase in permeation resistance value due to an increase in the design flux, and to reduce the operation cost. And by appropriately setting the stop water level for executing the stop step, the permeated water amount M (t) corresponding to the inflow amount Q (t-1) is secured, and at the same time, the overflow of the water to be treated from the membrane separation tank Exposure of the separation membrane to the air can be avoided.

  In the second characteristic configuration, as described in claim 2, in addition to the first characteristic configuration described above, the stop step has a permeation resistance value of the separation membrane equal to or higher than a preset upper limit allowable value. If it becomes, even if it is before the water level of one of the said water tanks falls to a setting water level, it exists in the point which pauses drawing | extracting of the permeated water from the said membrane separator.

  Even if the water level of any tank is higher than the set water level, if the permeation resistance value of the separation membrane exceeds the upper limit allowable value, a stop step is executed and an opportunity for cleaning the separation membrane can be secured, which can be dealt with in an emergency become.

  In the third feature configuration, in addition to the first or second feature configuration described above, in the stop step, the membrane separation device is aerated in the stop step and the treated water is directed upward. The point is to perform a relaxation step of cleaning the separation membrane by a flow.

  By forcibly executing the relaxation process in the stop step, the transmission resistance value can be lowered, and an unexpected sudden increase in the transmission resistance value can be avoided in advance.

  In the fourth feature configuration, as described in claim 4, in addition to the first or second feature configuration described above, in the stop step, a chemical solution cleaning step of cleaning the membrane separation device with a chemical solution is executed. There is in point to do.

  By forcibly executing the chemical cleaning step in the stop step, the permeation resistance value can be restored to a low state, and the membrane filtration step can be repeatedly executed in a stable state.

  In the fifth feature configuration, in addition to any one of the first to fourth feature configurations described above, the water level of the membrane separation tank is stopped after the stop step. When the membrane is restored to a predetermined water level higher than the water level, a preset time elapses, or a condition in which the permeation resistance value of the separation membrane decreases to a reference value lower than the upper limit allowable value is satisfied, the membrane The point is to return to the filtration step.

  Either when the water level in the membrane separation tank recovers to a predetermined level higher than the stop water level, when a preset time elapses, or when the permeation resistance value of the separation membrane decreases to a reference value lower than the upper limit allowable value It is preferable to return from the stop step to the membrane filtration step at the timing. When returning when the water level in the membrane separation tank is restored to a predetermined water level higher than the stop water level, it is possible to reliably avoid the occurrence of an inconvenient situation such that the liquid to be treated overflows from the membrane separation tank. When the time passes, the membrane can be stably washed during that time, and when the permeation resistance value of the separation membrane decreases to a reference value lower than the upper limit allowable value, the membrane can be reliably washed.

  In the sixth feature configuration, in addition to any one of the first to fifth feature configurations described above, the gain K is in a range of 1.01 <K <1.10. It is in the set point.

  By setting the gain in the range of 1.01 <K <1.10, an appropriate time balance between the membrane filtration step and the stop step can be realized, and a sufficient cleaning time can be obtained when the membrane is cleaned in the stop step. It becomes like this.

A first characteristic configuration of a membrane separation device according to the present invention is a membrane separation device for solid-liquid separation of water to be treated through a separation membrane, as described in claim 7, from the membrane separation device. A permeated water amount measuring unit for measuring the permeated water amount M (t), an inflow amount measuring unit for measuring the inflow amount Q (t) of the treated water, a water tank in which the membrane separation device is immersed, or the water tank, A water level measuring unit that measures the water level of a water tank that is in communication and has the same water level as the water tank, or a water tank into which overflow water flows from the water tank in which the membrane separation device is immersed, and the following equation M (t) = KQ (t-1)
M (t): Permeated water amount in period t having a predetermined length K: Gain (> 1)
Q (t-1): The permeated water amount is set so as to be represented by the inflow amount of the water to be treated in the period t-1 immediately before the period t, and the permeated water from the membrane separation device with the set permeated water amount. And a membrane filtration control unit that temporarily stops drawing of permeated water from the membrane separation device when the water level of any one of the water tanks falls to a preset stop water level.

  Even if the administrator does not manually perform the operation for membrane cleaning, the membrane filtration control unit automatically secures an opportunity for membrane cleaning at an appropriate interval.

  In addition to the first characteristic configuration described above, the second characteristic configuration further includes a permeation resistance value measuring unit that measures a permeation resistance value of the separation membrane, as described in claim 8, and the membrane filtration When the permeation resistance value of the separation membrane is equal to or higher than a preset upper limit allowable value, the control unit transmits permeated water from the membrane separation device even before the water level of any one of the water tanks drops to a set water level. It is in the point which pauses drawing of.

  In the third feature configuration, in addition to the seventh or eighth feature configuration described above, the membrane filtration control unit temporarily draws permeate from the membrane separation device. In the stopped state, the membrane separation device is aerated and the separation membrane is washed by an upward flow of the water to be treated, or the membrane separation device is washed with a chemical solution.

  As described above, according to the present invention, there are provided a method for operating a membrane separation apparatus and a membrane separation apparatus that can cope with an unexpected and sudden increase in differential pressure while increasing design flux and reducing operating costs. I was able to do it.

Illustration of wastewater treatment facility Illustration of membrane separator Illustration of membrane element (A), (b) is explanatory drawing of the operating method of a membrane separator (A), (b), (c) is explanatory drawing of the operating method of a membrane separator. Explanatory drawing of the waste water treatment facility which shows another embodiment Explanatory drawing of the waste water treatment facility which shows another embodiment

Hereinafter, a method for operating a membrane separator and a membrane separator according to the present invention will be described.
FIG. 1 shows an example of a wastewater treatment facility 1 in which a membrane separation device 7 is incorporated. An anaerobic tank 4 filled with activated sludge, an aerobic tank 5 provided with an air diffuser 5A at the bottom, and a biological treatment tank comprising a membrane separation tank 6; A membrane separation device 7 for obtaining permeated water from the water to be treated, a treatment water tank 8 for receiving the treated water filtered by the membrane separation device 7, and an operation control device C for controlling the state of the membrane separation device 7.

  Ammonia nitrogen contained in the raw water which is the treated water flowing into the anoxic tank 4 is nitrified to nitrate nitrogen in the aerobic tank 5 by the activated sludge and the organic matter is decomposed, and the downstream membrane separation tank 6 The solid-liquid separation is performed by the membrane separation device 7 disposed so as to be immersed.

Excess activated sludge contained in the to-be-treated water overflowed to the buffer tank 9 disposed adjacent to the membrane separation tank 6 is returned to the anoxic tank 4 together with nitrate nitrogen contained in the to-be-treated water by the pump P2. The denitrification process is reduced, and a part is extracted and discarded. The return amount R of activated sludge is set to about four times (R = 4Q _D ) with respect to the design inflow amount Q _{D of} raw water.

  The permeated water that has been solid-liquid separated by the membrane separation device 7 is stored in the treated water tank 8 and subjected to necessary treatment such as sterilization treatment, and then discharged into a river or the like.

  As shown in FIG. 2, the membrane separation device 7 has 100 plate-like membrane elements 7 </ b> B inside a membrane case 71 that is open at the top and bottom so that each membrane surface is in a vertical posture and about 6 mm to 10 mm. (In this embodiment, 8 mm) are arranged at regular intervals, and further, a diffuser 7A is provided below the membrane case 71.

  The air diffuser 7A includes an air diffuser 13 formed with a plurality of air diffusers, and is connected to an air supply source such as a blower B or a compressor installed outside the tank via an air diffuser header 14 connected to the air diffuser 13. Has been. In this embodiment, the blower B is used as an air supply source, and the air is supplied to the air diffuser 5A provided in the aerobic tank 5, and is also supplied to the air diffuser 7A via the valve V1. However, a dedicated blower may be provided for each of the diffuser 5A and the diffuser 7A so that the valve V1 is not used.

  A pump P1 as a suction mechanism installed outside the tank is connected to the membrane element 7B via a water collecting pipe 17, and the water to be treated in the tank is suction filtered so as to pass through the membrane surface of the membrane element 7B.

  As shown in FIG. 3, the membrane element 7 </ b> B has separation membranes 12 disposed on both front and back surfaces of a resin membrane support 10 having a length of 1000 mm × width of 490 mm via spacers 11. 13 is bonded to the membrane support 10 by ultrasonic waves or heat, or is bonded using an adhesive or the like.

  The separation membrane 12 is a microporous membrane having an average pore diameter of about 0.2 μm, and is an organic filtration membrane in which a nonwoven fabric is coated and impregnated with a porous resin. The membrane element 7B is not limited to such a configuration, and the separation membrane 12 is disposed so as to be wound on both the front and back surfaces of the membrane support 10, and the end of the separation membrane 12 is bonded or welded. Also good.

  A plurality of groove portions 10b having a depth of about 2 mm and a width of about 2 mm are formed along the longitudinal direction on the surface of the membrane support 10, and a horizontal groove portion 10c that communicates with each groove portion 10b is formed at the upper end portion thereof. Horizontal groove portions 10c formed on both front and back surfaces are communicated with each other via a communication hole 10d and communicated with a nozzle 10a formed on the upper edge portion of the membrane support 10.

  Each nozzle 10a is connected to a water collecting pipe 17 through a tube 16, and a pump P1 as a suction mechanism is connected to the water collecting pipe 17 so that permeated water sucked by the pump P1 is transferred to the treated water tank 8. It is configured (see FIG. 2).

  By operating the air diffuser 7A and the suction mechanism P1 of the membrane separation device 7 as described above, it is possible to obtain permeated water that allows the water to be treated to permeate the separation membrane 12.

  The operation controller C measures the amount of permeated water M (t) from the membrane separation device 7 and the amount of inflow measurement that measures the amount Q (t) of inflow water to be treated into the biological treatment tank 4. It comprises the part Q, the water level measurement part W which measures the water level of the buffer tank 9, and the membrane filtration control part 20 provided with the arithmetic processing function.

The membrane filtration control unit 20 has a permeated water amount M (t) in a period t having a predetermined length, an inflow amount Q (t-1) of treated water in a period t-1 immediately before the period t, and a gain K (K > 1), the following formula M (t) = KQ (t−1)
The permeated water amount M (t) is set so as to be expressed by the following equation, and the pump P1 is controlled so as to draw the permeated water from the membrane separation device 7 with the set permeated water amount M (t). When the WL drops to the preset stop water level LWL, the permeate drawing from the membrane separation device 7 is temporarily stopped.

  The membrane filtration control unit 20 aspirates the membrane separation device 7 with the drawing of permeate from the membrane separation device 7 temporarily stopped, and cleans the separation membrane by the upward flow of the water to be treated, or the membrane separation device. 7 is comprised so that it may wash | clean with a chemical | medical solution.

  When aeration is performed from the diffuser 7A with the pump P1 stopped, the water to be treated rises along the separation membrane 12, and fouling-causing substances such as microbial metabolites adhering to the surface of the separation membrane 12 in the process. As a result, the clogged state of the separation membrane 12 is reduced.

  A water stop valve V2 is provided between the water collecting pipe 17 and the pump P1, and a chemical liquid supply pipe connected to a chemical liquid tank (not shown) is branched and connected upstream of the water stop valve V2. After the pump P1 is stopped and the water stop valve V2 is closed, V3 is opened, and the separation membrane 12 is washed by supplying the solution to the membrane separation device 7 from the solution supply pipe. The chemical solution tank is filled with a chemical solution such as sodium hypochlorite.

  When the chemical cleaning is finished, filtration is performed by closing V3, opening the water stop valve V2, and driving the pump P1. At the initial stage of filtration, a bypass pipe is provided for removing permeate so as not to flow into the treated water tank 8 until the chemical solution flows out of the membrane separation device 7.

  A permeation resistance value measurement unit P that measures the permeation resistance value of the separation membrane 12 (pressure loss value of the membrane separation device) is further provided, and the membrane filtration control unit 20 has an upper limit allowable value in which the permeation resistance value of the separation membrane 12 is set in advance. If it becomes Pu or more, even if it is before the water level of the buffer tank 9 falls to the setting water level LWL, extraction of the permeated water from the membrane separator 7 is stopped temporarily.

  As shown to Fig.4 (a), an inflow fluctuation | variation is divided per 1 hour unit, and the permeated water amount M (t) is set with respect to the inflow amount Q (t-1) before 1 division. The permeated water amount M (t) is given by K · Q (t−1). As shown in FIG. 4 (b), when the inflow rate Q tends to increase, the amount of sludge retained in the system tends to increase, but when the inflow rate Q tends to decrease, the sludge amount retained in the system However, at a certain point in time, the amount of retained sludge becomes negative with respect to the initial value. The increase or decrease in the amount of retained sludge in the system appears as an increase or decrease in the water level in the buffer tank 9 and is detected by a water level gauge.

  The gain K is preferably set in a range of 1.01 <K <1.10, and an appropriate time balance between the membrane filtration step and the stop step can be realized, which is sufficient when the membrane is washed in the stop step. Cleaning time can be obtained.

  FIG. 4A shows an example in which the amount of raw water Q (t) flowing into the anaerobic tank 4 changes dynamically, and the amount of permeated water M (t) from the membrane separation device 7 changes with a delay. It is shown. As the membrane filtration proceeds, the filtration resistance gradually increases.

  If the operating flux is reduced by increasing the design flux of the membrane separation device 7 to reduce the total number of membrane separation devices 7, there is a risk of unexpectedly increasing the transmembrane pressure difference TMP.

  In the operation method of the wastewater treatment facility according to the present invention, the filtration operation is performed in a stable state without causing a rapid increase in the transmembrane pressure difference TMP. Hereinafter, the said operation method performed by the membrane filtration control part 20 is explained in full detail.

As described above, the membrane filtration control unit 20 uses the permeated water amount M (t) from the membrane separation device in the period t having a predetermined length to the biological treatment tank 4 in the period t-1 immediately before the period t. The inflow amount Q (t−1) of the water to be treated and the gain K (K> 1) are set so as to have the relationship represented by the following formula, and the permeation from the membrane separation device 7 with the set permeate amount. A membrane filtration step for drawing water and a stop step for temporarily stopping drawing of permeated water from the membrane separation device 7 when the water level in the buffer tank 9 is lowered to a preset stop water level LWL are executed.
M (t) = KQ (t-1)

  As shown in the above equation, by setting the gain K to be greater than 1 and setting the relationship so that the permeated water amount M (t) is delayed with respect to the inflow amount Q (t) of the water to be treated. During the execution of the membrane filtration step, a steady state in which the amount of activated sludge in the tank gradually decreases with the passage of time appears.

  In such a situation, when the stop step for temporarily stopping the permeate extraction from the membrane separation device 7 is executed, the water level in the buffer tank 9 gradually recovers, and during that time, the time for cleaning the separation membrane 12 is increased. It can be secured.

  It becomes possible to cope with an unexpected and sudden increase in permeation resistance value due to an increase in design flux, and it is possible to reduce operating costs by reducing the amount of aeration. And the permeated water amount M (t) corresponding to the inflow amount Q (t) can be ensured by appropriately setting the stop water level LWL for executing the stop step.

  When the water level in the buffer tank 9 drops to the stop water level LWL, the membrane filtration step is switched to the stop step. In the stop step, the permeation resistance value is lowered by performing a relaxation process in which the membrane element 7B of the membrane separation device 7 is aerated by the diffuser 7A and the separation membrane 12 is washed by the upward flow of the water to be treated. Thus, an unexpected and sudden increase in permeation resistance can be avoided.

  Further, in the stop step, by performing a chemical solution cleaning process for cleaning the membrane separation device 7 with a chemical solution, the transmembrane pressure difference TMP can be recovered to a low value close to the initial state, and the membrane filtration step in a stable state. Can be executed repeatedly.

  Which of the relaxation process and the chemical liquid cleaning process is executed in the stop step can be set as appropriate. For example, if the permeation resistance value of the separation membrane 12 measured by the permeation resistance value measurement unit P is equal to or greater than a predetermined threshold, the chemical cleaning step is selected, and if the permeation resistance value is less than the predetermined threshold, the relaxation step is set to be executed. be able to.

  Moreover, you may set so that a relaxation process may be preferentially performed only the preset predetermined number of times, and a chemical | medical solution washing | cleaning process may be performed at a subsequent stop step.

  FIG. 5A shows the characteristics of the transmission resistance value when the relaxation process is executed in the stop step (two-dot chain line) and the characteristics of the transmission resistance value when the relaxation process is not executed in the stop step (one-dot chain line). Are contrasted. The separation membrane 12 is washed each time the relaxation process is performed in the stop step, and the degree of contamination is reduced, so that the permeation resistance value increases gradually and membrane separation can be performed stably for a long time. Similar characteristics can be obtained even when the chemical cleaning step is performed with a low concentration chemical instead of the relaxation step.

  FIG. 5B shows the permeation resistance value characteristic (two-dot chain line) when the chemical solution washing process is executed with a high concentration chemical solution at the stop step, and the permeation resistance value when the relaxation process is not executed at the stop step. The characteristics (dotted line) are contrasted. When the permeation resistance value exceeds a predetermined threshold value and the chemical solution washing process is executed in the stop step, the separation membrane 12 is washed to the initial state, thereby suppressing an increase in permeation resistance value and stably maintaining the membrane for a long time. It becomes possible to separate. In addition, you may comprise so that a chemical | medical solution washing | cleaning process may be performed uniformly irrespective of a threshold value.

  FIG. 5C shows the characteristics of the permeation resistance value (two-dot chain line) when the above-described relaxation process and the chemical solution cleaning process are combined, and the characteristics of the permeation resistance value when the relaxation process is not executed in the stop step (one point). A chain line) is contrasted. The chemical solution cleaning process is performed after the relaxation process is performed a plurality of times in the stop step. Thus, membrane separation can be stably performed for a long time by combining the relaxation step and the chemical solution washing step.

  Moreover, you may comprise so that the density | concentration of the chemical | medical solution used at a chemical | medical solution washing | cleaning process may be switched between light and shade. For example, a mode in which low concentration chemical cleaning is performed in a stop step up to a predetermined number of times and high concentration chemical cleaning is executed after a predetermined number of times may be repeated. In this case, the same characteristics as in FIG.

  When the permeation resistance value of the separation membrane 12 is equal to or higher than a preset upper limit allowable value, the permeation water drawing from the membrane separation device 7 is temporarily stopped even before the water level of the buffer tank 9 is lowered to the set water level LWL. Preferably, a stop step is performed.

  Even when the water level of the buffer tank 9 is equal to or higher than the set water level, when the permeation resistance value of the separation membrane 12 exceeds the upper limit allowable value, a stop step is executed, and an opportunity for cleaning the separation membrane 12 can be secured, so that an emergency can be dealt with. It becomes possible.

  After execution of the stop step, the water level in the buffer tank 9 is restored to a predetermined water level NWL higher than the stop water level, and a preset time Δt has elapsed, or the permeation resistance value of the separation membrane 12 is lowered to a reference value lower than the upper limit allowable value. It is preferable to return to the membrane filtration step when any of the decreasing conditions is satisfied.

  When the water level in the buffer tank 9 is restored to a predetermined level higher than the stop water level, the pump P2 can be prevented from being idle, and when the preset time elapses, the membrane can be stably washed during that time. When the permeation resistance value of the separation membrane is reduced to a reference value lower than the upper limit allowable value, the membrane can be reliably washed.

  In the example shown in FIG. 1, the buffer tank 9 is provided adjacent to the membrane separation tank 6, but in the membrane separation tank 6 not provided with the buffer tank 9, the water level is restored to a predetermined water level higher than the stop water level. It is preferable to configure so as to return to the filtration step when it is done.

  FIG. 6 shows another embodiment of the wastewater treatment facility. In the above-described embodiment, the wastewater treatment facility including the aerobic tank 5 in which the diffuser 5A is installed at the bottom and the membrane separation tank 6 in which the membrane separation apparatus 7 is immersed is described. Further, the aerobic treatment and the membrane separation treatment may be realized in the same treatment tank by using the membrane separation tank 6 together.

  FIG. 7 shows another embodiment of the wastewater treatment facility. In the embodiment described above, an example in which raw water directly flows into the anoxic tank 4 on the upstream side constituting the activated sludge treatment tank has been described, but a bar screen 2a and the like for removing contaminants mixed in the raw water are provided. A pretreatment tank 2 and a flow rate adjustment tank 3 for temporarily storing water to be treated from which impurities have been removed by a bar screen 2a or the like may be provided. Even when the inflow of raw water fluctuates, the water to be treated at a constant flow rate is stably supplied from the flow rate adjustment tank 3 to the activated sludge treatment tank 4 by the flow rate adjustment mechanism P3 such as a pump or a valve. .

  In the above-described embodiment, an example in which the activated sludge treatment tank including the anaerobic tank 4, the aerobic tank 5, and the membrane separation tank 6 is a series is described. However, the waste water in which a plurality of activated sludge treatment tanks are arranged in parallel. It goes without saying that the present invention can be applied even to a processing facility, in which case there is no need to execute the membrane separation step and the stop step in synchronization with each series, and each series independently. The membrane separation process and the stop process may be executed.

  In this case, the operation control device C may be provided in each series, or only the membrane filtration control unit 20 may be configured to be shared.

  The above-described embodiment is one aspect of the present invention, and the present invention is not limited by the description. Specific configurations and control aspects of each part can be appropriately changed and designed within the scope of the effects of the present invention. Needless to say.

1: Wastewater treatment equipment 4: Anoxic tank 5: Aerobic tank 5A: Aeration device 6: Membrane separation tank 7: Membrane separation device 7A: Aeration device 8: Treated water tank 20: Membrane filtration control unit C: Operation control device

Claims (9)

An operation method of a membrane separation device for solid-liquid separation of treated water through a separation membrane,
The permeated water amount M (t) from the membrane separator is expressed by the following equation M (t) = KQ (t−1)
M (t): Permeated water amount in period t having a predetermined length K: Gain (> 1)
Q (t-1): Set to have a relationship represented by the inflow amount of the water to be treated in the period t-1 immediately before the period t, and draw out the permeate from the membrane separation device with the set permeate amount. A membrane filtration step;
A water tank in which the membrane separation tank device is immersed, a water tank that communicates with the water tank and has the same water level as the water tank, or a water tank into which overflow water flows from the water tank in which the membrane separation apparatus is immersed. A stop step for temporarily stopping drawing of permeated water from the membrane separator when the water level drops to a preset stop water level;
A method for operating a membrane separation apparatus.   In the stop step, when the permeation resistance value of the separation membrane is equal to or higher than a preset upper limit allowable value, the permeation from the membrane separation device is performed even before the water level of any one of the water tanks falls to the set water level. The method of operating a membrane separation apparatus according to claim 1, wherein water drawing is temporarily stopped.   The operation method of the membrane separation device according to claim 1 or 2, wherein in the stopping step, a relaxation step is performed in which the membrane separation device is aerated and the separation membrane is washed by an upward flow of water to be treated.   The method for operating a membrane separation device according to claim 1 or 2, wherein a chemical solution cleaning step of cleaning the membrane separation device with a chemical solution is executed in the stopping step.   After execution of the stop step, the water level of the water tank whose water level was detected in the stop step is restored to a predetermined water level higher than the stop water level, a preset time has elapsed, or the permeation resistance value of the separation membrane is the upper limit The method for operating a membrane separation device according to any one of claims 1 to 4, wherein when any of the conditions for lowering to a reference value lower than an allowable value is satisfied, the process returns to the membrane filtration step.   The operating method of the membrane separation apparatus according to any one of claims 1 to 5, wherein the gain K is set in a range of 1.01 <K <1.10. A membrane separation apparatus for solid-liquid separation of water to be treated through a separation membrane,
A permeated water amount measuring unit for measuring a permeated water amount M (t) from the membrane separator;
An inflow measuring unit for measuring the inflow Q (t) of the treated water;
Water level of a water tank in which the membrane separation device is immersed, a water tank communicating with the water tank and having the same water level as the water tank, or a water tank into which overflow water flows from the water tank in which the membrane separation device is immersed A water level measurement unit for measuring
The following formula M (t) = KQ (t−1)
M (t): Permeated water amount in period t having a predetermined length K: Gain (> 1)
Q (t-1): The permeated water amount is set so as to be represented by the inflow amount of the water to be treated in the period t-1 immediately before the period t, and the permeated water from the membrane separation device with the set permeated water amount. A membrane filtration control unit that temporarily stops drawing of permeated water from the membrane separation device when the water level of any one of the water tanks is lowered to a preset stop water level;
A membrane separation apparatus. Further comprising a permeation resistance value measurement unit for measuring the permeation resistance value of the separation membrane,
When the permeation resistance value of the separation membrane is equal to or higher than a preset upper limit allowable value, the membrane filtration control unit is configured to remove the water level of any one of the water tanks from the membrane separation device even before the water level drops to a set water level. The membrane separator according to claim 7, wherein the permeated water is temporarily withdrawn.   The membrane filtration control unit is configured to aerate the membrane separator and wash the separation membrane with an upward flow of water to be treated in a state where drawing of permeate from the membrane separator is temporarily stopped, or the membrane separation The membrane separation apparatus according to claim 7 or 8, wherein the apparatus is washed with a chemical solution.

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